content: /*
   * Copyright 2016-present David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package hu.akarnokd.rxjava3.operators;
  
  import java.util.concurrent.atomic.AtomicBoolean;
  
  import org.reactivestreams.*;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.processors.AsyncProcessor;
  
  /**
   * Cache only the very last value and relay/replay it to Subscribers.
   *
   * @param <T> the value type
   * @since 0.15.0
   */
  final class FlowableCacheLast<T> extends Flowable<T>
  implements FlowableTransformer<T, T> {
  
      final Publisher<T> source;
  
      final AsyncProcessor<T> processor;
  
      final AtomicBoolean once;
  
      FlowableCacheLast(Publisher<T> source) {
          this.source = source;
          this.processor = AsyncProcessor.create();
          this.once = new AtomicBoolean();
      }
  
      @Override
      public Publisher<T> apply(Flowable<T> upstream) {
          return new FlowableCacheLast<>(upstream);
      }
  
      @Override
      protected void subscribeActual(Subscriber<? super T> s) {
          processor.subscribe(s);
          AtomicBoolean o = once;
          if (!o.get() && o.compareAndSet(false, true)) {
              source.subscribe(processor);
          }
      }
  }
  